1. Technical Field
The present invention relates to a linear vibrator.
2. Description of the Related Art
A vibration motor is a part which converts electric energy into mechanical vibration using the generating principle of electromagnetic force, and is mounted on a mobile phone to be used as a mute call indicating means. As the market for mobile phones is growing rapidly and a variety of functions are being added to the mobile phone, the parts of the mobile phone are being required to be miniaturized and of high quality. Thus, a new structure for a vibration motor, which overcomes the drawbacks of the conventional vibration motor and dramatically improves the quality of the conventional vibration motor, is required.
In recent years, as many mobile phones coming onto the market have large LCD screens and the mobile phones have adopted a touch screen manner, the use of a vibration motor to generate vibrations when a touch screen is touched has increased. Especially, the vibration motor for generating vibrations when the touch screen is touched must meet the following requirements. First, as the number of times the vibration motor is used to generate vibrations when the touch screen is touched is larger than the number of times the vibration motor is used to generate vibrations when a call is received, a long operating lifespan is required. Second, the vibrational response must become fast according to the speed at which the screen is touched, thus providing a high sense of satisfaction to the user who is touching the touch screen and feeling the vibrations.
A conventional vibration motor which has been widely used generates rotating force and rotates a rotary part using an eccentric mass, thus obtaining mechanical vibrations. The rotating force undergoes commutation through a contact point of a brush and a commutator, so that an electric current is supplied to a rotor coil. However, the brush type motor using the commutator is problematic in that, when the motor is rotated, the brush passes through a gap between segments of the commutator, thus causing mechanical friction and electric sparks, leading to abrasion, or generating impurities such as black powder and thereby shortening the lifespan of the motor.
Further, when a voltage is applied to the motor, it takes a long time to reach a target amount of vibrations because of the inertia of the rotary unit having the eccentric mass, so that the response becomes slow and thus it is difficult to realize vibrations suitable for a touch screen phone.
In order to overcome the drawbacks of lifespan and response and to realize the vibrating function of a touch screen phone, linear vibrators are widely used.
The linear vibrator does not use the rotating principle of a motor, but is excited by an electromagnetic force having a resonance frequency which is determined using a spring installed in the vibrator and a movable unit hanging on the spring, thus generating vibrations. Here, the electromagnetic force is generated when a magnet placed on a moving mass part interacts with the direct current or alternating current having a predetermined frequency of a coil placed on a support plate.
However, the linear vibrators which are being applied currently are generally located at the corner of a mobile phone, thus generating vibrations in a vertical direction relative to an LCD screen. The linear vibrator has an outer diameter of about 10 mm and a thickness of about 4 mm. However, the thickness of a linear vibrator designed to vibrate in a vertical direction is limited because a mass body installed in the vibrator must be able to be displaced vertically in a space having a thickness of about 4 mm in order to generate vibrations. Since the mounting space of a mobile phone is limited, using an increase in the thickness of the linear vibrator so as to obtain a desired amount of vibrations is limited.
In order to overcome the problems, the mass body in the linear vibrator may be constructed to move in a horizontal direction relative to the LCD screen of the mobile phone. The horizontal movement has a smaller spatial limitation, in comparison with the vertical movement. Further, it is relatively easy to realize a vibrator having a length of from 8 to 12 mm which is larger than the vertical thickness of about 4 mm.
Therefore, the present invention is intended to protect a coil lead wire from irregular movement when a mass body vibrates, in a linear vibrator constructed to have a thickness which is equal to or smaller than the conventional linear vibrator and constructed so that the mass body moves in a horizontal direction so as to improve a sensible amount of vibrations in a mobile phone.